/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.ListIterator;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A list iterator which forwards all its method calls to another list iterator. Subclasses should
 * override one or more methods to modify the behavior of the backing iterator as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>{@code default} method warning:</b> This class forwards calls to <i>only some</i> {@code
 * default} methods. Specifically, it forwards calls only for methods that existed <a
 * href="https://docs.oracle.com/javase/7/docs/api/java/util/ListIterator.html">before {@code
 * default} methods were introduced</a>. For newer methods, like {@code forEachRemaining}, it
 * inherits their default implementations. When those implementations invoke methods, they invoke
 * methods on the {@code ForwardingListIterator}.
 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingListIterator<E extends @Nullable Object>
        extends ForwardingIterator<E> implements ListIterator<E>
{

    /**
     * Constructor for use by subclasses.
     */
    protected ForwardingListIterator()
    {
    }

    @Override
    protected abstract ListIterator<E> delegate();

    @Override
    public void add(@ParametricNullness E element)
    {
        delegate().add(element);
    }

    @Override
    public boolean hasPrevious()
    {
        return delegate().hasPrevious();
    }

    @Override
    public int nextIndex()
    {
        return delegate().nextIndex();
    }

    @CanIgnoreReturnValue
    @Override
    @ParametricNullness
    public E previous()
    {
        return delegate().previous();
    }

    @Override
    public int previousIndex()
    {
        return delegate().previousIndex();
    }

    @Override
    public void set(@ParametricNullness E element)
    {
        delegate().set(element);
    }
}
